1. Field of the Invention
This invention relates to a valve timing controller and, more particularly, to a valve timing controller for controlling the valve timing of an intake valve and an exhaust valve for a valve train of an internal combustion engine.
2. Description of the Related Arts
A prior art of the valve timing controller of this kind is disclosed in Japan Patent Laid-open Publication H09-60508 (published on Mar. 4, 1997). In this prior art, the valve timing controller is disposed in the driving force transmitting system transmitting the driving force from the drive shaft of an internal combustion engine (a crankshaft of the engine) to the driven shaft (camshaft) opening and closing either an intake valve or an exhaust valve of the internal combustion engine. The valve timing controller in this prior art comprises a housing member rotating in one unit with the drive shaft (or the driven shaft), a rotor member assembled at a pair of shoe portions provided in the housing member for relative rotation therewith at a hub portion, forming an advance angle fluid chamber and a retard angle fluid chamber at a vane portion, and rotating in one unit with the driven shaft (or the drive shaft), a stopper mechanism defining the initial phase of the housing member and the rotor member, a lock mechanism defining the relative rotation of the housing member and the rotor member at the initial phase, and a hydraulic pressure circuit controlling the supply and exhaust of the operation fluid to the advance angle fluid chamber and the retard angle fluid chamber and controlling the lock/unlock of the lock mechanism.
In the valve timing controller of above mentioned prior art, a stopper mechanism is adopted which includes a stopper surface provided on the circumferential direction end of the shoe portion (the portion rotatably supporting the rotor member) of the housing member and a contacting surface provided on the circumferential direction end of the vane portion (the portion forming the advance angle fluid chamber and the retard angle fluid chamber with the shoe portion) of the rotor member. The initial phase of the housing member and the rotor member is defined by the contact between the stopper surface and the contacting surface.
The lock mechanism of above-mentioned prior art comprises a piston assembled slidably in axial direction of the camshaft in an accommodation hole disposed in the vane portion of the rotor member and having a tip end tapered off, a tapered hole disposed in the housing member and being capable of tapered fitting with the tip portion of the piston at the initial phase of the housing member and the rotor member, and a spring biasing the piston towards the tapered hole. By tapered fitting of the tip of the piston and the tapered hole at the initial phase of the housing member and the rotor member, the relative rotation between the housing member and the rotor member is restricted and the relative rotation between the housing member and the rotor member is allowed under the condition that the tip portion of the piston is separated or retrieved from the tapered hole.
However, the valve timing controller of the prior art has the following disadvantages: Since the contacting surface (the end surface in circumferential direction) provided on the vane portion of the rotor member contacts the stopper surface (the end surface in circumferential direction) provided on the shoe portion of the housing member, high precision machining is required on the end surface in circumferential direction of the shoe portion of the housing member and on the end surface in circumferential direction of the vane portion of the rotor member. The vane portion of the rotor member and the shoe portion of the housing member are required to have enough strength to bear against the load at contacting.
Having the initial phase of the housing member and the rotor member as a standard, that is, for the manufacturing precision of the stopper surface formed on the shoe portion of the housing member and of the contacting surface formed on the vane portion of the rotor member, severe tolerance of the relative position between the tip portion of the piston and the tapered hole is required (Since the piston is a separated member from the member formed with the contacting surface and the stopper surface and the tapered fitting portion is provided at the different location from the contacting portion of the stopper surface and the contacting portion, it is very difficult to satisfy the highly required precision). Since the relative rotation of the housing member and the rotor member is allowed when the tip portion of the piston is separated or retrieved from the tapered hole, in the case the external materials entered into the tip portion of the piston which has been separated from the tapered hole (since the tip portion of the piston is tapered off, a large gap is generated between the piston and the accommodation hole, and the external materials is easy to be entered), such external materials tend to be trapped between the tip portion of the piston (tapered tip end portion) and the accommodation hole.
Accordingly, an object of the valve timing controller of the invention is to reduce the size, improve the productivity and achieve reliable operation.
To solve the aforementioned problems the following technical means is provided with a valve timing of the invention provided on the driving force transmitting system transmitting the driving force to the driven shaft opening and closing either intake valve or an exhaust valve of an internal combustion from the drive shaft of the internal combustion engine, a housing member rotatable in one unit with the drive shaft (or the driven shaft), a rotor member rotatably assembled with a pair of shoe portions provided on the housing member, forming an advance angle fluid chamber and a retard angle fluid chamber at a vane portion, and rotating in one unit with the driven shaft (or the drive shaft), a stopper mechanism defining the initial phase of the housing member and the rotor member, a lock mechanism restricting the relative rotation of the housing member and the rotor member at the initial phase, and a hydraulic pressure circuit controlling the supply and exhaust of the operation fluid to the advance angle fluid chamber and the retard angle fluid chamber and controlling the lock/unlock of the lock mechanism. The stopper mechanism and the lock mechanism include a lock member slidably assembled with the housing member (or the rotor member) and the tip portion of the lock member which is always projecting towards the rotor member (or the housing member), a free recess portion formed in the rotor member (or the housing member) and accommodating the tip portion of the lock member while allowing the relative rotation of the housing member and the rotor member, a stopper surface formed on the end surface in circumferential direction of the free recess portion and defining the initial phase by the contact with the tip portion of the lock member, a lock recess portion formed continuously along the stopper surface and being capable of accommodating the tip portion of the lock member with restricting the movement thereof in circumferential direction at the initial phase, and a lock spring biasing the lock member towards the lock recess portion.
In this case, it is desirable to form a second stopper surface limiting the maximum relative rotation of the rotor member relative to the housing member on the other end surface in the circumferential of the free recess portion opposite to the stopper surface.
The valve timing of the invention includes a first rotation body opening and closing either the intake valve or the exhaust valve of the internal combustion engine, a second rotation body rotating in one unit with the drive shaft of the internal combustion engine and transmitting the driving force from the drive shaft to the first rotation body, a phase change controlling means changing the phase of the first rotation body either to the advance angle side or to the retard angle side relative to the second rotation body, and a restricting means including a stopper mechanism regulating the rotational amount of the first rotation body relative to the second rotation body at least to either side of the advance angle side and the retard angle side and a lock mechanism restricting the relative rotation of the first rotation body and the second rotation body. The stopper mechanism and the lock mechanism of the restricting means are formed in one unit.
In this case, the first rotation body and the second rotation body are coaxially arranged. It is desirable that the restricting means is comprised of a lock member rotatably and slidably disposed on one of the first rotation body and the second rotation body, the free recess portion provided on the other of the first rotation body and the second rotation body and accommodating the lock member while allowing the relative rotation of the first rotation body and the second rotation body, the stopper surface provided on one end surface in circumferential direction of the free recess portion and restricting the rotation of the first rotation body relative to the second rotation body in either direction of the advance angle side and the retard angle side by being connected to the lock member, the lock recess portion provided continuously along the stopper surface and being capable of accommodating the lock member to restrict the relative rotation between the first rotation body and the second rotation body, and a biasing means always biasing the lock member towards the lock recess portion.
The effects of the technical means in the invention of the valve timing are as follows. Since the stopper mechanism and the lock mechanism including the lock member, the free recess portion, the stopper surface, the lock recess portion, and the lock spring are provided on the housing member and the rotor member, machining on the end surface in circumferential direction of the shoe portion of the housing member and on the end surface in circumferential direction of the vane portion of the rotor member is not required, and the vane portion of the rotor member and the shoe portion of the housing member are not required to have an excess strength. Accordingly, the manufacturing cost can be reduced and the size of the valve timing controller can be reduced by making thinner vane portion of the rotor member.
Since the stopper surface defining the initial phase, by the contact with the tip portion of the lock member is formed on one end in circumferential direction of the free recess portion and the lock recess portion is formed continuously along the stopper surface (since the stopper surface and the lock recess portion are formed at one place on the same member), severe tolerance of the relative position of the lock recess portion relative to the initial phase can be easily achieved. Accordingly, the productivity of the valve timing controller of the invention can be improved.
Since the tip portion of the lock member which is always projecting and a small gap will be sufficient for allowing the sliding movement between the lock member and the housing member (or rotor member) slidably supporting the lock member, the external materials rarely enter into the gap, and the entrapment of the external materials can be prevented. This improves the locking operation reliability of the lock member.
When the second stopper surface restricting the maximum relative rotational amount of the rotor member relative to the housing member is formed on the other end surface in circumferential direction of the free recess portion opposite to the stopper surface at the practical use of the invention, the maximum rotational amount of the rotor member relative to the housing member can be precisely and easily set by precisely forming the length in circumferential direction of the free recess portion.